8.3 Perform Quality Control Process

Perform Quality Control makes sure that the project's deliverables comply with the quality requirements and prevents noncompliance issues from recurring.

There are only a handful of project management processes that have deliverables as their outputs, and it’s sometimes easy to confuse their different purposes.

While the Verify Scope and Perform Quality Control processes both examine the deliverables, quality control ensures that the deliverables meet the quality requirements while scope verification ensures that the deliverables meet the scope requirements.

The deliverables, quality checklists, quality metrics, and the quality management plan are the main inputs to the quality control process.

QC also makes sure that defects have been brought back into quality compliance.

Defects are treated as change requests through integrated change control and the deliverables are re-validated through Perform Quality Control, and if the defect repair is successful then the change control system serves as the notification that the correction is completed.

Quality control processes occur throughout the project from its early stages all the way to the end as long as project processes are executing there will always be corresponding quality control processes.​

QC activities are usually performed by trained personnel from the performing organization's Quality Control Department, but the project team will need to fill this role if no quality control personnel exist.

Perform Quality Control Process Decomposition

Perform Quality Control Process Decomposition

Perform Quality Control Process: inputs

  • Project management plan
    The quality management plan describes how quality control processes will be performed and what levels of quality must be met.
  • Quality metrics
    Quality metrics are the specific quality goals the project must meet and how the quality control processes will confirm compliance.
    Quality metrics can include any type of applicable measurement, including defect rates, bug rates, failure rates, uptime, reliability, and coverage area.
  • Quality checklists
    Quality checklists are documents that outline the key steps that must be performed as part of quality control.
    Checklists are "to-do" lists that ensure that everything is performed and in the correct order.
  • Work performance measurements
    These are performance measurements that are communicated to stakeholders and include items such as planned versus actual performance for the schedule, cost, and quality.
  • Approved change requests
    Approved changes from integrated change control can impact quality control activities. Deliverables that initially fail quality control and need reworked are technically changing requests, so those deliverables may also be resubmitted to quality control as an approved change request.
  • Deliverables
    Quality control is performed against the deliverables.
  • Organizational process assets
    The organization may have defect reporting or other procedures that must be followed.

Perform Quality Control Process: Tools and Techniques

  • Cause and effect diagrams
    A cause and effect diagram shows what factors can be contributing to an issue or problem. It's also known as a fishbone diagram or an Ishikawa diagram.
  • Control charts
    A control chart is a type of run chart that is used to determine whether a process is in control or out of control. The control chart is also known as the Shewhart chart, named after Walter Shewart who first developed them in the 1920s. If a process is in control, the chart can be used to accurately determine future performance.
  • Flowcharting
    A flowchart graphically illustrates the steps, sequences, and decision points in a process.
  • Histogram
    A histogram is a column chart that shows a collection of measurements grouped into categories, and it helps identify trouble-spots.
  • Pareto chart
    A Pareto chart is a histogram chart showing the values in descending order. By illustrating the data in this manner, the chart can be used to hone in on the factors causing the biggest impact.
  • Run chart
    A run chart is a line graph that displays measurements over time. Run charts are sometimes also referred to as run-sequence plots and they help to detect trends or changes in output, performance, or quality.
  • Scatter diagram
    A scatter diagram is a graph that uses Cartesian coordinates to display values for two variables. By viewing the plotted measurements for both variables, a relationship, if one exists, can be determined.
  • Statistical sampling
    Statistical sampling is a broad term that involves choosing random, representative samples for testing rather than testing each individual deliverable.
  • Inspection
    Inspection activities are the testing, measurement, review, and examination of the deliverable to determine whether it's in compliance with the quality requirements.
    The inspection methods used will differ depending on the deliverable types.
  • Approved change request review
    Deliverables that initially failed quality control are submitted to integrated change control as for change requests. If approved for correction, this review ensures that the rework performed has been done as requested.

Perform Quality Control Process: Outputs

  • Quality control measurements
    These are the measurements and results from activities that make sure the deliverables meet the quality requirements.
  • Validated changes
    Any approved changes (such as rework) are re-validated to make sure the change was implemented as requested.
  • Validated deliverables
    Validated deliverables have been checked to ensure that they meet the quality requirements.
  • Organizational process assets updates
    Lessons learned, completed checklists, root-cause analysis, and other quality control activities result in updates to organizational process assets.

Quality Control Terminology

The project team will need to have a general understanding of statistical quality control and terminology so that they can work with and properly evaluate the quality control outputs.

Prevention

Prevention keeps non-compliance issues from happening in the first place.

While it's good to catch a defect before it gets into the hands of the customer, it's even better to prevent the defect from occurring at all.

Prevention of errors is always preferable to reliance on inspection, and this philosophy is the basis of the PMBOK's project quality management and of quality management in general.

Prevention activities involve looking at processes for factors that can potentially lead to defects, and when defects are detected, determining the root causes so that those factors can be mitigated.

Unfortunately, not all defects can be definitively prevented, but we still need to investigate and understand the reasons for the failure.

Inspection

Inspection activities are the testing, measurement, review, and examination of the deliverable to determine whether it's in compliance with the quality requirements.

The inspection methods used will differ depending on the deliverable types.

For example, the inspection methods employed against software will be different than those performed for a medical device.

Inspection is meant to keep the defect out of the hands of the customer, and when non-compliance issues are found, the root cause is determined so that it can be prevented in the future.

Accuracy and Precision

Accuracy describes how close a measurement is to its true value while precision describes how repeatable the measure is and how many significant digits it’s measured in.

Though we often use the two terms interchangeably, in the scientific and statistical realms, they describe different characteristics because a measurement can be accurate and precise, precise but not accurate, or accurate but not precise.

Tolerances

Tolerances are the acceptable variations in limits, such as a fluorescent light bulb should burn between 4000 and 5000 continuous hours. They define the maximum variations from a nominal value that are acceptable because they will have a negligible effect on the quality level.

Special and Common Causes

A Special Cause is an unusual event outside of the process that leads to a measurable change in the process (such as an increase in production downtime).

Though unusual, special causes are considered preventable.

For example, a backup generator failed to start up during a power failure.

The failure of the backup generator can be prevented in the future through regular mechanical maintenance and operational tests.

A Common Cause is a normal event within the process that leads to a measurable change in the process (such as an increase in production downtime).

Common causes result in rare, but tolerable variations. Even if it were possible to remove all possible common causes from a process, the effort to do so would usually have cost prohibitive.

Common causes are thus generally considered as non-preventable and accepted as part of the process.

Control Limits

Control limits are the upper and lower limits set for a process, usually at three standard deviations from the mean, and determine whether a process is in control or out of control.

Control Chart

Control limits are used with control charts.

Sampling

Statistical sampling is a broad term that involves choosing random, representative samples for testing rather than testing each individual deliverable.

There are many different sampling techniques that can apply to different disciplines, industries, and deliverables.

The main key to this technique is to make sure that the sample collected is representative of the whole population.

When properly sampled, this method takes less time than measuring the whole population.

Attribute sampling of the deliverable results in it either passing if it conforms to requirements or failing if it does not, while variable sampling passes or fails based on an overall degree of conformity to the requirements.

For example, a bicycle inner tube either holds air or it leaks, in which case that inner tube would fail through attribute sampling.

Contrast that to a food manufacturing process in which a sample bag from an entire production run of a batch of potato chips is tested for overall weight, crispness, taste, texture, and color.

If the sample bag chosen is within tolerances for those characteristics then the entire batch passes.

Statistically Independent and Mutually Exclusive

When the outcomes of processes have no relationship between each other, they are considered statistically independent.

The errors in an order entry process won't have any correlation to the mechanical breakdowns of a truck in the transportation system.

When one choice excludes another, the choices are said to be mutually exclusive.

Choosing to replace a metal-based product component with a plastic-based component negates any options that involve using an aluminum-based component.

Standard deviation is used to measure how data is organized, and it involves a formula that results in a mathematical description of how diverse the data is.

Standard deviation is shown graphically as a bell curve, and it's used in quality for establishing quality levels and process control limits.

For the PMP examination, we should know the basic standard deviation formula, the concept of standard deviation and what it's used for, and the four main sigma values for normally distributed data.

Standard deviation formula is the result of the optimistic estimate subtracted from the pessimistic estimate, divided by six:

(Pessimistic – Optimistic)/6

Quality Control Tools

Cause and Effect Diagrams

 A cause and effect diagram shows what factors can be contributing to an issue or problem.

It's also known as a fishbone diagram or an Ishikawa diagram (named after Kaoru Ishikawa).

Cause and Effect Diagram

Cause and Effect Diagram

Cause and Effect Diagrams Technique:

  • Identify the problem or issue, and place it as the "head" of the fishbone.
  • Pose the problem or issue as a question to the group and explore the contributing causes and factors.
  • As broad categories become known evident, add them as side branches to the categories.
  • As possible contributing factors within categories are found, add these as underlying branches beneath the categories.
  • Further question the group on contributing factors because there may be more details and factors involved.
  • When the diagram is completed, the group can use it to validate assumptions, prioritize actions to eliminate contributing factors and develop an action plan.

Run charts

A run chart is a line graph that displays measurements over time. Run charts are sometimes also referred to as run-sequence plots.​

Run Chart

Run Chart

Run charts help to detect trends or changes in output, performance, or quality, and once a change is detected then they can also be used to help determine the exact timing of when the change occurred.

Control charts

A control chart is a type of run chart that is used to determine whether a process is in control or out of control.

The control chart is also known as the Shewhart chart, named after Walter Shewart who first developed them in the 1920s.

If a process is in control, the chart can be used to accurately determine future performance.

Control Chart

Control Chart

Control charts use upper control limits (UCL) and lower control limits (LCL), which are collectively known as natural process limits.

As data is collected on the run chart, if the measures fall within the upper and lower control limits then the process is considered to be in control.

Measurements outside the control limits mean the process is out of control and the cause needs to be found. An in-control process implies neither an efficient nor a quality process.

In fact, the Rule of Seven states that if there are seven consecutive measurements that fall on one side of the mean then there's an assignable cause that needs to be investigated because something has changed in the process.

The rule of seven applies even if the measurements are still within the control limits.

Flowcharts

A flowchart graphically illustrates the steps, sequences, and decision points in a process.

Flowchart

Flowchart

It can be helpful for defining the logic and flow in a new process, but it's also helpful to diagram existing processes to look for contention or relationships in the process.

Histogram

A histogram is a column chart that shows a collection of measurements grouped into categories, and it helps identify trouble-spots.

Histogram

Histogram

For example, a histogram could show the number of help desk support calls over a period of time grouped by the days of the week.

Parteto Chart

A Pareto chart is a histogram chart showing the values in descending order. By illustrating the data in this manner, the chart can be used to hone in on the factors causing the biggest impact.

Parteto Chart

Parteto Chart

The chart is named after Pareto's 80/20 rule, and in the case of a Pareto chart, it helps us find the 20% of the factors that are likely causing 80% of the problems.

Scatter Diagram

A scatter diagram is a graph that uses Cartesian coordinates to display values for two variables.

By viewing the plotted measurements for both variables, a relationship, if one exists, can be determined.

Scatter Diagram

Scatter Diagram

For example, a scatter diagram that plots inclement weather as one variable and late deliveries as another variable might show that there's a relationship between bad weather and delivery delays.

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